A modified technique for isolating epithelial cell nuclei from rat mammary gland.

A modification of the technique of Minasian and Jabara (1) is described for obtaining a higher yield of virgin rat mammary epithelial cell nuclei of greater purity. Modifications include the introduction of 0.32 M sucrose into the mammary epithelial cell-homogenizing medium and the addition of 0.05% Triton X-100 for 30 min to the crude nuclear pellet. The isolated nuclei were judged to be of acceptable purity by the virtual absence of specific cytoplasmic enzyme activities in biochemical assays and in the DNA, RNA, and protein contents of the preparations. However, electron microscopy revealed some residual contamination by cytoplasmic fragments and substantial numbers of mast-cell granules.